Recent Flooding in Pahiatua and Future Flood Modelling

Mother nature has certainly made her presence known during August with rivers close to the 2004 flood levels.

With a district as large as ours often one part can bear more of the force whilst others in the community carry on with life as normal. Pahiatua bore the brunt of the heavy rain two weeks ago and we saw homes that were flooded as sections and streets flooded early in the morning.

This rain event was fast and traumatic for those who experienced flooding. The Huxley Street drain and the town creek have been problematic over many years and are both natural watercourses with environmental considerations required regarding clearing.

The agreed maintenance which clears rubbish, vegetation and spraying were all carried out. The drain could not cope with the intensity and volume of the rainfall that we seem to be experiencing more frequently.

We will discuss the level of service during our next Infrastructure Climate Change and Emergency Management Committee meeting to check if this is adequate or if anything more could be done.

It was the first test for the new culvert placed by Waka Kotahi to assist with water flow from the Huxley Street drain. Our team’s focus is looking at longer term options to address the flow of stormwater before it gets into the township which means diverting water above the town from the upper catchment.

There are several ways to do this, but each comes with a large price tag. It is a balance when we are required now to plan infrastructure for 200-year storm events, hair raising when what we experienced recently in Pahiatua was a 1 in 30 year event. Our weather is changing at a rate we are struggling to keep up with.

The most important piece of work funded through our Long-Term plan is the flood modelling work that will enable detailed modelling to be done for the whole district’s stormwater. The findings of this study will inform the strategy for what kind of stormwater systems should be built, and where. We also have an inflow and infiltration programme that is focussed in Eketāhuna because stormwater getting into the wastewater system equates to us needing to process more water than we need.

This results in additional cost in both processing and consenting. These are all big pieces of work from a very specialised and highly skilled team within the Tararua Alliance. People will often hear me say of the three waters, stormwater is the most difficult to deal with. Like many other rural areas, stormwater is our least developed. Resilience to climate change is a key driver for this study.

We look forward to sharing this work even though the costs will be eye-watering to us all, it demonstrates the need for a changed model for our stormwater through “Local Water Done Well”. We know that good planning and technology works, and it was heartening to see the bio gardens do their job well preventing flooding in the Main Street of Pahiatua.

You can help by not dumping rubbish or garden clippings in drains that disrupt water flow during these events and by reporting any issues through as a customer request via phone or our Antenno app.

During any weather event, please know that our phone lines are open 24/7 and all calls assist us in co-ordinating our response and crews. My grateful thanks to those team members and the public who all stepped in to help clear, clean, and keep each other safe.